The art has long sought an economical way to handle the known problems of "kink" in the I-V curves of partially depleted SOI transistors and of parasitic latchup, both of which are related to the fact that the body of SOI transistors is floating unless it is connected to a potential.
In addition, fully depleted N-channel SOI MOSFETs suffer from low drain breakdown voltage that is due to the existence of an inherent parasitic n-p-n bipolar transistor effect, as reported by E. P. Ver Ploeg, et al in IEDM '92, page 33.
Various methods of making a contact to the body of a SOI transistor are known, but have various disadvantages such as reducing the amount of current that can be handled with a given transistor width or of taking up an excessive amount of space.